1. Field of the Invention
The present invention relates in general to a field programmable logic and analogic integrated device and in particular to an integrated logic circuit programmable for substantially constituting a state machine capable of driving a digital-analog converter (DAC) and analog circuits which interacts with said state machine.
2. Description of the prior art
Programmable (and erasable) logic devices (PLD), based upon the use of EPROM or EEPROM cell arrays, are known and widely used for implementing on a single chip a large number of logic functions which would otherwise be normally implemented by "dispersed logic circuitry" needing a large number of normal, nonprogrammable, logic devices. PLDs represent powerful tools for implementing so-called "state machines". These in turn represent reliable general-purpose building blocks for constructing sequential digital systems, reducing the overall amount of logic circuitry needed. In particular state machines offer valid solutions for a wide range of control functions, for example, in complex interface systems.
There is however an area of applications for digital techniques wherein the "microprocessor" still appears a necessary choice. This is the case, for example, of control and/or regulation systems for analog functions or devices wherein analog signals must be converted by means of an analog/digital converter (ADC) into digital signals which may be read and processed by a microprocessor in order to produce digital signals which may, where necessary, be converted back into analog signals by means of a digital/analog converter (DAC). For a large number of applications, this architecture of control and/or adjustment circuits, though powerful and effective, is intrinsically wasteful because of its "rigidity", determined by the fact that the flow of signals through a microprocessor system is at any instant essentially monodirectional. The microprocessor because of the versatility which characterized it, may carry out a limited number of standard operations. Moreover this "rigidity" of a microprocessor control system implies a processing time which is often nonnegligeable for the objectives of the overall control system. Furthermore in many cases the use of such a powerful tool such a microprocessor appears entirely unjustified for the type of control operation to be performed and it is indicative to this respect the increasing demand for microprocessors with an extremely limited number of bits, which are sought for such relatively simple control or regulation systems.